Summary of Work: The pharmacological and physiological activity of recently developed opioid analogues were determined in mice. The bioactivity profile paralled that of the in vitro pharmacological data and reflected the receptor binding affinity (see previous projects for details). Some synthetic analogues which exhibited agonism were weaker than the control substances (deltorphin for delta or morphine for mu receptors); however, some were substantially better (2- to 25-fold) than morphine in generating analgesia using standard testing procedures. In fact, these compounds are under patent application in Japan and disclosure at this time would jepardize that process.